1. Field of the Invention
The subject invention relates to an antenna, specifically a microstrip patch antenna, for receiving and/or transmitting a circularly polarized radio frequency (RF) signal.
2. Description of the Related Art
Patch antennas for receiving circularly polarized RF signals are well known in the art. One example of such an antenna is disclosed in U.S. Pat. No. 5,270,722 (the '722 patent) to Delestre. The '722 patent discloses an antenna including a first radiating layer and a second radiating layer disposed substantially parallel to and apart from each other. Each radiating layer is almost square in shape but two opposite sides are slightly concave (with the other two opposite sides being straight). The second radiating layer is rotated 90° with respect to the first radiating layer such that the concave sides of the second radiating layer align with the straight sides of the first radiating layer, and vice versa. A first transmission line is connected to a center of one of the straight sides of the first radiating layer and a second transmission line is connected to a center of one of the straight sides of the second radiating layer. Because two sides of the second radiating layer are concave, the first transmission line may approach the first radiating layer perpendicularly without coming into contact with the second radiating layer.
Although the antenna of the '722 patent can receive and/or transmit circularly polarized RF signals, the antenna requires a pair of transmission lines to feed the antenna. There remains an opportunity for a patch antenna having two radiating layers which requires only one transmission line.